The present invention relates to devices that incorporate superabrasive materials, and methods for the production and use thereof. Accordingly, the present invention involves the fields of chemistry, physics, and materials science.
A variety of abrasive and superabrasive tools have been developed over the past century for performing the general function of removing material from a workpiece. Actions such as sawing, drilling, polishing, cleaning, carving, and grinding, are all examples of material removal processes that have become fundamental to a variety of industries.
A number of specific material removal applications require the use of superabrasive tools. In these cases, the use of conventional abrasive tools may be infeasible due to the nature of the workpiece, or the surrounding circumstances of the process. For example, activities such as cutting stone, tile, cement, etc. are often cost prohibitive, if not impossible to accomplish, when attempted using a conventional saw blade. Additionally, the economy and performance of other material removal activities may be increased when using superabrasive tools, due to their greater durability.
One common way in which superabrasive materials have been incorporated into a tool is as superabrasive particles. In this case, the superabrasive particles are most often embedded in a matrix, such as a metal matrix, and held in place by the mechanical forces created by the portion of the matrix directly surrounding the particles. A variety of consolidation techniques, such as electroplating, sintering, or hot pressing, a matrix around superabrasive particles are known. However, because the matrix surrounding the superabrasive particles is softer than the superabrasive particles, it wears away more quickly, during use, and leaves the diamond particles overexposed, and unsupported. As a result, the diamond particles become prematurely dislodged and shorten the service life of the tool.
A number of attempts have been made to overcome the above-recited shortcoming. Most notably, several techniques that attempt to chemically bond the superabrasive particles to the matrix, or other substrate material, have been employed. The main focus of such techniques is to coat or otherwise contact the superabrasive particle with a reactive element that is capable of forming a carbide bond between the superabrasive particle and the metal matrix, such as titanium, chromium, tungsten, etc. Examples of specific processes include those disclosed in U.S. Pat. Nos. 3,650,714, 4,943,488, 5,024,680, and 5,030,276, each of which are incorporated herein by reference. However, such processes are difficult and costly for a variety of reasons, including the highly inert nature of most superabrasive particles, and the high melting point of most reactive materials.
Further, the melting point of most reactive metal materials is well above the stability threshold temperature of most superabrasives. To this end, the method by which the reactive material may be applied to the superabrasives is generally limited to either solid-state reactions or gas reactions that are carried out at a temperature that is sufficiently low so that damage to the diamond does not occur. Such processes are only capable of achieving a monolithic coating, and cannot produce an alloy coating. While the strength of the carbide bonds yielded using these techniques generally improves particle retention over mere mechanical bonds, they still allow superabrasive particles to become dislodged prematurely.
Another method of forming carbide bonds is by using a braze alloy that contains a reactive element. The braze alloy is consolidated around the superabrasive particles by sintering. One example of a specific process of this type is found in U.S. Pat. No. 6,238,280, which is incorporated herein by reference. While such processes may yield a tool that has greater grit retention than tools having no chemical bonding of the superabrasive particles, as a general matter, solid-state sintering of the braze alloy only consolidates the matrix material, and does not attain as much chemical bonding as the solid and gas state deposition techniques.
Additionally, the use of conventional braze may be limited, as it generally also serves as the matrix material for the body of the tool. Most braze alloys are ill equipped to act as a bonding medium and simultaneously act as the matrix material, due to the specific characteristics required by each of these elements during use. For example, in order to achieve greater carbide bonding, some superabrasive particles may require alloys that are too soft for the intended tool application. A matrix that is made of a material that is too soft may wear away too quickly and allow the superabrasive particles to dislodge prematurely.
As such, superabrasive tools that display improved superabrasive particle retention and wear characteristics, including methods for the production thereof, continue to be sought through ongoing research and development efforts.
Accordingly, the present invention provides superabrasive tools having improved superabrasive particle retention, and methods for the making thereof As a basic component of such tools, the present invention additionally provides a coated superabrasive particle having improved retention properties when incorporated into a tool. In one aspect, the coated superabrasive particle may include a superabrasive particle, and a solidified coating of a molten braze alloy that is chemically bonded to the superabrasive particle.
In one aspect of the invention, a coated superabrasive particle may be made by the basic steps of: covering the superabrasive particle with the braze alloy in a molten liquid state, and solidifying the liquid braze alloy around the superabrasive particle. Due to the liquid state of the alloy, it is able to wet the superabrasive particle and spread over the surface thereof. As a result, chemical bonds are formed at the interface of the metal and the superabrasive particle, which provide a bonding strength of about 5 to 10 times greater than that achieved with either electroplating or sintering. Hence, when used in a superabrasive tool, the superabrasive grit can protrude further out of the support material and achieve a higher rate of material removal. Furthermore, tool life is lengthened because the rate at which superabrasive grits are pulled out of or dislodged from the support material is significantly slowed.
There has thus been outlined, rather broadly, various features of the invention so that the detailed description thereof that follows may be better understood, and so that the present contribution to the art may be better appreciated. Other features of the present invention will become clearer from the following detailed description of the invention, taken with the accompanying claims, or may be learned by the practice of the invention.